High-speed commutators for switching units



June 2, 1964 R. A. AUSFELD HIGH-SPEED COMMUTATORS FOR SWITCHING UNITS 7 M A n 1 c 5 N /T a 5N a m Mm v -uw MN 1 A A 4 h a H W d 7 m m June 2, 1964 R. A. AUSFELD HIGH-SPEED COMMUTATORS FOR SWITCHING UNITS Filed July 19, 1962 4 Sheets-Sheet 2 1% do /f A. Awe/d INVENTOR.

y/zbdJ- j 7 WNW June 2, 1964 R. A. AUSFELD HIGH-SPEED COMMUTATORS FOR SWITCHING UNITS Filed July 19, 1962 4 Sheets-Sheet 5 W V dm W M /T P. w W cum; m 5 wmfi m 1, 4 A a 7/ w y M o W U 0 R i E T 1\ Es y 1 a w w June 2, 1964 R. A. AUSFELD HIGH-SPEED COMMUTATORS FOR SWITCHING UNITS Filed July 19, 1962 4 Sheets-Sheet 4 ATTOR/Vfy United States Patent Filed July 19, 1962, Ser.No. 216,951 11 Claims. c1. zen-s Mechanical Research, Inc, Sarasota, Fla, :1 corpora- This invention generally relates to commutators and more particularly to rotary commutators especially suitable for'efiiciently commutating low level signals derived from low-valued impedance sources.

In many systems, for examplein telemetry, the output signals of one or more transducer sources, of thermocouples, photocells, strain gauges, accelerometers, etc.,

must be successively applied to one or more utilization networks. Often this is accomplished by coupling the transducers signals with said network or networks through a mechanical commutator. Typically, the values of the respective transducers impedances and signal levels are relatively low. Good switching action requires, especially when commutating low level signals, that the commutator introduce only negligible distortions, else the ensuing error signals may blank out the transducers intelligence signals being commutated. 7

Generally, known prior art terns or commutators were undesirably limited in one more of the following respects: s

('1) Severe environmental service conditions, as high temperatures, vibrations and shock, deleteriously affected the switching action; v i

(2) The switching action, by the switching member over the stationary switch contacts, consisted at least in part mechanical switching sysof'a sliding action which produced relatively high values of edge noise, contact noise and contact resistance; and

(3) The sliding action in turn gave rise to metallic "ice 7 mutator includes a rotatable shaft, a rotor assembly carrymg a rotatably mounted roller, and a stator assembly comprising at least one segmented ring carrying a plurahty of contacts. To assure that the roller maintains a pure rolling action over the contacts, the segmented ring has a homologous surface engageable with the roller. A new and improved pump provided with a filter removes most foreign particles from the liquid. The pump is mounted for cooperation with and close to the contacts and wear particles, the accumulation of which resulted after a sufiiciently longv time in short-circuited contacts.

Accordingly, it is a general object of the present invention to provide new and improved commutators which largely overcome the aforesaid and other apparent limitations of prior art commutators I It is another object of this invention to provide new and improved commutators'which are especially suitable for eflicien'tly commutating, without introducing appreciable distortions, the outputs of signal sources whose impedances and signal levels are relatively low.

It is a further object of this invention to provide new and improved commutators. of the foregoing character which are adapted to operate reliably even under relatively severe physical environmental conditions.

It is a still further object of this invention toprovide new and improved commutators of the foregoing character which are capablev of maintaining, without substantial impairment, their original switching characteristics during a relatively long operating life. H I,

Broadly, the above and other apparent objects of this invention are achieved by providing a mechanical commutator in which substantially pure rolling, and no sliding action takes place between the contacts and the switching member, thus causing a minimum of wear on the contacting surfaces between the contacts andtlie switching member. Afiuid contact cleaner, preferably liquid, is employed for constantly maintaining a-high inter-contact insulation resistance. Preferably, the inter-contact separations or slots are made oblique relative to the line of contact between the contacts surface and the switching mem-' her. The slanting of the slots assures a smooth andmore uniform switching action. g I

In the preferred embodiment'of the invention, the comthe roller.

These and other features of my invention'will be apparent from the following detailed description of a preferred form of my invention taken in conjunction with the accompanying drawings wherein:

. FIG. 1 is a sectional elevation view of a preferred form v of the invention;

FIG. 2 is a plane view of a commutator stator in plane 2-2 of FIG. 1;

PEG. 3 is a cross-sectional view along line 33 of FIG. 2;

FIG.' 4 is a sectional elevation view of the roller of FIG. 1;

FIGS. 4A and 4B are helpful in explaining the operation of the rolling and switching actions;

FIG. 5 is a top view of the rotor assembly in plane 5-5 of FIG. 1;

of FIG. 10; and

FIG. 12 is a sectional View in the plane iz-l2 of FIG. 10'.

Referring now to the drawings, the commutator, constructed in accordance with this invention, generally designated as 20, is enclosed in a cylindrical housing 21 made of a light metal such as aluminium. The space inside the housing is divided into two compartments 22 and 23: the former including the commutators driving means such as electric motor 24, and the latter the commutators rotary and stationary parts.

Frame25, bolted to shoulder 26 of housing 21, fixedly supports the commutators stationary parts. Housing 21 is made fluid-tight by two end covers 27, 28, each associated with an '0 ring 29. Connector 30, centrally mounted in cover 2'7, receives the motors energizing power. By supporting the motors free end, bracket 31 avoids undesired radial vibrations.

Centrally situated within compartment 23 is the comrnutators main shaft 32. The shaft carrying the commutators rotary parts has each of its ends, respectively, rotatably mounted within bearings 33, 34. For stable and efficient commutation, the shafts motion should be limited to pure rotation about its axial axis XX. This can be accomplished, for example, by carefully machining the commutators parts, by selecting proper bearings and by coupling the motors shaft 35 to the commutators shaft 32 with a properly designed coupling device 36. Coupling 36. includes two shaft couplings 37 between which is sandwiched a vibration eliminating and torque transmitting member 38, preferably made of nylon. Member 33 has, in each of two mutually perpendicular planes, two torque transmitting tongues axially extending from each of its flat faces.

' the number of'poles they contain.

commutator 26*, in addition to consecutively establishing, for example, an electric circuit between a common line and a plurality of separate lines, is also often required to furnish synchronizing pulses. The synchronizing pulses are derived from onev or more, typically two, magnetic pickup heads. Each pickup head cooperates with a row of axially extending pins arranged around a circumference on a matrix rotor 41. For example, the outer row may have forty-four pins such as 40 and the inner row only one pin 40'. However, to simplify the drawing, only one magnetic pickup head 39 is shown adjacently mounted opposite to a pin 40 of the outer row. In a well-known manner, the pickup head 39 comprises a flux carrying air gap. A pulse is induced in a winding on the core of the pickup head each time a magnetic pin sweeps past the cores air gap. A stationary magnetic shield 42 is provided for eliminating possible stray magnetic fields.

Commutators are commonly classified depending upon The commutators shaft 32 in the embodiment of FIG. 1 illustratively carries four such poles 43 grouped into two pairs. To keep the commutators internal surfaces free of wear particles, a fluid contact cleaner, preferably a liquid, is circulated and filtered by pump 46. For greater efiiciency, a pair of back-to-back pumps 46 is co-operatively mounted with each pair of poles 43. Each pump 46 comprises a stator 47, a rotor 48 and a filter 49. In accordance with a feature of this inventionflhe four poles 43 are grouped into two units 50. Each such unit 50 is fixedly secured to frame 25 by a plurality of screws 51 and includes two pump stators 47 sandwiched between two commutator stators 44.

Each commutator stator 44, shown in greater detail in FIGURES 2 and 3, includes a cylindrical brace 53 havingnear its periphery several apertures 52 for receiving the mounting screws 51. Brace 53 is made of a nonmagnetic material such as brass. Concentrically mounted within brace 53 are a collector ring 54 and a segmented contact ring 55, both of which are made of a good conductor of electricity such as silver. Rings 54, 55 are embedded in a hard insulating filler 56 and are mounted in spaced relationship in planes normal to the shafts main axis XX. Filler 56 should have a coefficient of thermal expansion on the same order of magnitude as the coefficient of thermal expansion of rings 53-55. To obtain a more rigid mounting, rings 5355 are respectively provided with shoulder 57 and grooves 58, 59. Before embedding the rings in the filler 56, the internal peripheral surfaces '76, 77 of rings 54, 55 are made frusto-conic: surfaces 76', 77' are engendered by the revolution of an inclined line ZZ, intersecting axis XX at an angle La-7,

A number of narrow slots 69 are provided extending radially between the fiat faces of ring 55, a distance I1 from the rings outer circumferential periphery. Distance h is less than the width of ring 55 for reasons which will become apparent subsequently. To the collector ring of employed poles 43. Each connector 66 includes a number of pins 65', one for each active contact 65, and a pin 61' for the collector ring 54. To simplify the drawing, only three pins 65 are shown per connector 66. By means of wires 67, pins 65' are connected to their corresponding contacts 65, and pins 61' are connected to their corresponding rings 54 via wires 61.

The function of each pole 43 is to establish periodically and successively an electric circuit between the common pin 61' and each of pins 65'. The desired switching or commutation is accomplished by utilizing a rotating 7 frusto-conic roller 45.

As shown in FIG. 4, roller 45 is rotatably mounted on its shaft 70, each end of which is housed in bearings 71. Mounted on bearings 71 are: a cylindrical support tube 72, the frusto-conic roller proper 73 and, to insulate frustum 73 from tube 72, an insulating sleeve 74. Thus, frustum 73 is electrically insulated from any other member of the roller assembly 45. To allow for a better engagement between the, slanted surfaces of the roller and of rings 54, 55, there is provided on the external surface of frustum 73 a groove 75, as shown, thereby defining on 54 is soldered a rigid conductor 61, preferably of silver,

extending through an insulating bushing 62 housed in the annular brace 53. After embedding rings 5355 in filler 56, in any well-known manner, surface 77. of the contact ring 55 is then'provided with slots 64, each extending to and lining up with a corresponding radial slot 60. Each slot 64 is slanted at an angle 12 with a plane passing through a corresponding adjacent radial slot 60. After cutting outwardly slot 64 in the above-described manner to join with the radial slots 65), it will be apparent that the annular ring 55 will consist of a'number (ninety in the preferred embodiment illustrated in FIG. 1) of commutator segments or contacts generally designated as '65, each insulated from its next adjacent segments by an insulating layer of the filling material 56.

Centrally mounted within the right-end cover 28 are a number of connectors 66 corresponding to the number the frustum 73 two slanted surfaces 76, 77. Surfaces '76, 77 are preferably made substantially as wide as their opposite frusto-conic surfaces 76', 77' on rings 54, 55, respectively. To avoid the establishment of an appreciable layer or film of fluid between the oppositely engaging frusto-conic surfaces, the material employed for making frustum 73 should be porous. In the illustrated embodiment, the employed material was bronze although other materials, such as copper, steel, etc., may also be utilized.

The rollers shaft 70 is mounted so that its axis Y-Y forms an angle c with the commutators main axis XX. Shaft 70 is fixedly mounted to a rotor assembly 100, subsequently dtscribed by means of collars 78, 79. The "free ends of support arms 78', 79 extend through their corresponding collars 78, 79 and through bores at each end of shaft 70, as shown. Arms 78, 79 are mounted in parallel but opposite directions so as to provide a constant resilient bias for urging roller 45 against its opposite mating rings 54, 55.

FIGURE 4A shows that by extending surfaces 76', 77' there is formed a cone O RV an, similarly, by extending surfaces 76, 77 there is formed a cone O RW. As can be seen, the cones apexes O and O coincide. As a result, no sliding but only pure rolling action takes place between the respectively engaging frusto-conic surfaces 76, 76' and 77, 77'. p V 7 Pure rolling action takes place when no one point of one surface comes in contact with two successive points of a corresponding engaging surface. On the other hand, if a point on one member comes in contact with all successive points of the acting surface of the other member then the action is said to be pure sliding. Combined rolling and sliding action takes place where a pair of surfaces roll upon each other With some slipping. There are several types of curved members which when paired can give pure rolling action: for example, two contacting cylinders rotating on each other about their parallel axes without slipping yield pure rolling action. On the other hand, two rolling hyperboloids without slipping may also yield pure rolling action.

In the preferred embodiment, however, the stator and the roller are given frusto-conic surfaces. In this case, it can be established readily that for pure rolling action to take place, the apexes of the extended two cones O RV and O RW must coincide, as shown in FIG. 4A. Frustoconic engaging surfaces are selected in the preferred embodiment because they can be easily machined and fur-. ther because their engagement imposes upon the roller a self-biasing force which tends to stabilize the switching action. This can readily be illustrated as follows: the resultant force P, exerted by the spring arms 78', 79' against the commutator stator 44, is shifted by the angle a from a vertical plane normal to the main axis XX.

, Hence force P can be resolved into a horizontal component H and a normal component N. Asa result, to disengage roller 45 from its mating stator 44, a stray force, which may be caused by vibration, shock, etc., must first overcome the self-biasing forces Hand N. The derived advantage from the coincidence of both cones O RV and O RW is that no special spring biasing means are required for urging roller 45 against its mating rings 54, 55. In addition, because arms 78', 79' are mounted in opposite directions, any tendency of one of the arms to cause one of the cones ends to disengage from its corresponding mating ring is immediately compensated by a'counter force, developed by the other arm. This counter force is normally sufiicient to maintain roller 45 in continuous rolling contact with stator 44.

As shownin FIGURES 4A, 4B, the common surface between roller 45 and rings 54, 55 is at all times limited to a straight line ZZ. As roller 45 rotates around its axis Y-Y, line ZZ engenders the conic surface Q RV at an angular velocity depending upon the rollers speed. Because slots 64 are slanted with respect to radial slots 60, roller 45 leaves each contact 65 gradually: as line ZZ rotates around main axis XX in the direction of the arrows, roller45 first engages a switch contact only at a point P while distributing most of its pressure along segment P P on the next precedingswitch contact, thereby maintaining the physical integrity of each switch contacts edges. Gradually; as line "ZZ rotates, the rollers pressure shifts from the preceding contact to the following contact. Thus by slanting the inter-contact slots, a smoother switching action is obtained and, therefore, contact bounce which plagued prior art commutators is substantially eliminated in accordance with this feature of the invention.

In the preferred embodiment an active switch contact, designated as 6511, had a length 1 and a blind switch contact, designated as 651), hada comparatively shorter length d The blind and the active contacts were alternately disposed on ring 54. The blind contacts areprovided in order to'avoid make-before-break switching action, however, if such action were desired,

then all contacts would bemade active, that is, wires 67 would then be connected to each of the switch contacts instead of only to the alternate ones 65a. It will be understood that the contacts can be rearranged to accommodate, for various switching patterns.

As previously mentioned, the material used for making the frusto-conic member 73 of roller 45 is porous.

Consequently, the resilient biasing force P- urges the liquid, which would ordinarily form an insulating film ,between surfaces 76', 77' and their corresponding surfaces 76, '77, to penetrate into the microscopic pores of frusturn 73, thereby breaking the insulating film and assuring'sulrlcient rolling friction between roller 45 and its mating'rings 54, 55.. Also because the cones O RV and O RW have a common apex, the rollers pure rolling motion is kinematically balanced thusavoiding sliding or 1 in pairs.

tric strength, (2) be chemically stable over the operating temperature range typically between -55 C. to 100 C, and over expected variations of pressure and, (3) have a low and substantially uniform Viscosity over the expected temperature range. Such liquids are available commercially under the name of silicon oils. One such 'to establish an insulating film between the rolling surfaces. It is desired that the liquid act only as a flushing agent for washing away the microscopic particles adhering to thecomrnutators parts and particularly to the rolling surfaces.

It should be noted that lubrication of the rolling surfaces '76, 77 and '76, 7'7 is not necessary, inasmuch as rolling friction must be continuously maintained therebetween. Moreover, by employing a liquid contact cleaner, the generated microscopic metallic particles become distributed over the entire liquids volume. To clean the liquid and to circulate decontaminated liquid between the commutators rolling surfaces, one or more pumps combined with'filters are provided.

A detailed description of a pump 46 will now be given. As shown in FIGURES 9-12, the pumps are arranged Such a pair includes a pair of stators 47, mounted back-to-back, cooperating with a corresponding pairof rotors 48. Each stator 47 has the form of a relatively thin fiat annular disc defining an outer cylindrical surface 87, an inner cylindrical surface 38, and two plane faces 85, 86. Near the peripheral surface $7 are symmetrically disposed around a circumference several bores 89 for receiving the mounting screws 51. On face $5 is grooved, concentric with shaft32, an annular channel 90 of the liquid employed, may include surgical cotton 91,

a suitable filter paper 92, and a fine screen 93. The discs inner cylindrical face 88 is subdivided into a number of sections 94, each acting as an independent small pump. Each section 94 includes two. radially extending slots 95,} 95, the former extending throughthe thickness of the disc from face 85 'to face 86 for a radial distance I1 and the latter extending from face 86 an axial distance I1 and a radial distance h thus joining slot 96 with channel 90, as shown in FIG. 9. Extending from face 86 and from slot 95 is an arcuate channel 97, limited by walls 98 and 99. Channel 97 has a length M, shorter than length L of section 94 but long enough to include the opening to slot 96. Hereinafter slot 95 will be referred to as the pumps inlet port and the slot 96 as its outlet slipping action which otherwise would produce excessive wear on the roller 45 and the commutator stator 44.

But'eventhough in the commutator of this invention contact wear is at a minimum, microscopic metallic particles may still be produced during the switching action and, if not removed, may deleteriously affect the commutation function. These particles tend, after a sufficient- 1y long time, to reduce the inter-contact insulation resistance and eventually to even short-circuitadjacent switch contacts 65a and 6512. Also, these particles tend to adhere to the rolling surfaces and, if not removed,

would tend to produce increased contact resistance, con-7 tact noise, contact bounce, and contact Wear. Often,

the particles adherence may even causeskidding of. the

roller.

To avoid the above and other apparent highly undesirable effects, commutator 20 is filled with a liquid contact cleaner. The liquid should (1) have a high dielecport. The pumps rotor 48 is an annular member having a height h and a width slightly larger than the width of stator 47. Rotor 48 forms, preferably, integral part with a frame 101, subsequently described.

. When a relative velocity between the pumps stator 47 and its corresponding rotor 48 exists, there appears a pressure difference between the inlet and outlet. ports 95,

96 which is directly proportional, for a particular fluid,

. to the average relative velocity, the length M of channel 97, and the existing rolling coefficient of friction. This pressure difference, however, is also inversely proportional to the square of the distance h the height of channel 97. Hence, the smaller distance h is, the greater the pressure, differentials between the inlet and outlet ports will be. Distance [17 may typically be on the order of .002 inch. Inasmuch as the difference in pressure is proportional to the length M of channel 97, it would appear that the fewer the number of sections 94 is, the

' greater will be the magnitude of obtainable pressure differentials. On the other hand, the greater the number of pump'sections 94 is, the better the filtering action of less. Moreover, as previously mentioned, the magnitude of the pressure differentials increases with the relative velocity between the pumps stator 47 and rotor 48, hence greatergfiuid flow and filtering action exist when mostly needed.

As shown in FIGURES 8, the pumps rotor 48 preferably forms integral parts with frame 101 of the commutators rotor assembly 100. Frame 101 is fixedly secured to the main shaft 32 by two set screws (not shown) threaded into apertures 102. Adjustably mounted onto frame 101 is a roller carriage 103. Frame 101 has two axially extending rectangular bores 104 for receiving corresponding rectangular guiding posts 105 which are fastened to a retaining plate 106, housed in a recess 107, by a screw 108. Axially extending from the roller carriage 103 are two clamps 109, 110, the former extending to a higher elevation than the latter in order to provide the rollers shaft 70 with the desired inclination angle 0 relative to the commutators main shaft 32. Roller carriage 103 is kept in vertical alignment by means of bolts 111, extending through the guiding posts 105. The rollers arms 78, 79' are respectively secured to clamps 110, 109 by means of screws 112, thereby allowing the roller to maintain the desired pressure P against the frusto-conic surfaces 76 77' of rings 54, 55, respectively. It will be appreciated from the flexibility afforded by rotor assembly 100 that roller 45 can be accurately positioned with respect to its engaging mating rings 54, 55.

In operation of the commutator 20, after motor 24 becomes energized, the rotation of its shaft 35 is transmitted to the commutators shaft 32. Because rolling friction exists between roller 45 and surfaces 76', 77' on mating rings 54, 55, respectively, the roller starts rotating around its axis 70 at a speed dependent upon the speed of shaft 32. As roller rotates around its axis Y-Y, its line of contact ZZ also rotates thereby successively establishing contact between the stators collector ring 54 and each of the stators contacts 65. A typical electric circuit can be traced out as follows: from a pin 65', wire 67, corresponding segment or contact 65, surfaces 77', 77, 75, 76 and 76', lead 61 and back through a wire 67 to a common terminal 61'. Thus, each separate line connected to each pin 65 of each pole 43 becomes periodically connected through a commutator pole 43 to the common line connected to pin 61.

In'operation of the pump 46, as the rotor 48 turns, the liquid surrounding it begins to revolve also. The liquid enters inlet port 95 and, due to its viscosity, is dragged along the arcuate shallow channel 97 at a speed dependent primarily upon the difference in pressure existing between the inlet and outlet ports 95, 96. The raised surface 9? acts as a gate to prevent the further flow of the liquid and to force it to travel the course of least impedance, i.e., to enter outlet port 96. Thus, practically, the outlet port 96 provides the sole exit for the circulating liquid. After the liquid flows out through channel 96, it is filtered by filtering means 49 which captures the fluids impurities.

Since a pair of pumps 46 is housed between a pair of poles 43, the pumps can effectively circulate clean liquid between the poles rolling surfaces. The circulation of liquid increases with the speed of motor 24 thereby responding to the filtering needs of commutator 20.

Although the liquid flushes the commutators rolling surfaces, it does not establish an appreciable insulating film on :them since the rollers pressure P and the liquids viscosity are such that the establishmentof any such film engaging surfaces; the existence of rolling instead of sliding action greatly eliminates the amount of switching noise; by engaging and disengaging each contact segment gradually, an appreciable decrease of contact-bounce is obtained; and by employing small and yet very efiicient, practically wearless pumps, the detergent fluid is always maintained clean, the contact-resistance is kept uniform,

and the commutator assured a relatively long operating life.

While a preferred embodiment has been disclosed, it will be understood by one skilled in the art that modifications may be made therein without departing from the principles of the present invention, and said invention is to be limited only by the claims appended hereto. For example, various types of materials and fluids may be utilized. Further, the converse mode of operation may be adopted, that is, the stators can be made rotary and the rotors stationary or, the rotors and stators can both be rotatable provided a relatively velocity is maintained therebetween. Also, the number of contacts can be arranged to produce a variety of switching patterns, and the commutation can be madeto result in make-beforebreak, etc. The commutator may be operated very satisfactorily at low as well as at normally high speeds.

What is claimed is:

1. A commutator comprising:

a housing, a rotatable main shaft in said housing, at least one switching unit concentrically mounted with the axis of said shaft, said switching unit comprising a commutator ring and a rotatably mounted frustoconic roller, said commutator ring carrying a plurality of insulated, conducting, arcuate segments; a relatively low viscosity liquid substantially filling said housing;

a pump having a cylindrical rotor and an annular stator both concentrically mounted with the axis of said main shaft, said rotor fitting inside said rotor and being separated therefrom by a narrow gap sufficient to allow for the frictional circulation of said fluid between the outer rim of said rotor and the inner rim of said stator; and I i said stator comprising at least one inlet port, at least one outlet port, and a filter spaced in the path of liquid flow from the outlet port to the inlet port for removing foreign particles from said liquid;

2. A commutator comprising: 1

a housing, a rotatable main shaft in said housing, at least one switching unit concentrically mounted with the axis of said shaft, said switching unit comprising a commutator ring and a rotatably mounted frustoconic roller, said commutator ring carrying a plurality of insulated, conducting, arcuate segments, a relatively low viscosity liquid substantially filling said housing;

a pump having a cylindrical rotor and a flat annular stator concentrically mounted with the axis of-said main shaft; one flat face of said rotor defining an annular filtering channel extending approximately through half of the thickness of said rotor, said filtering channel including filter means;

said stator having an inner rim defining several friction channels each having an inlet port for admitting fluid tosaid friction channel and an outlet port communicating with said filtering channel, and

said rotor being mounted inside said stator and being 9 separated therefrom by a narrowgap sufficient to allow for the frictional Circulation of fluid between said inlet port and said outlet port upon the occurrenceof a relative rotation between said rotor and said stator. V I r 3. A rotary commutator comprising in combination: housing, a low viscosity fluid filling said housing, a rotatable main shaft in said housing, at least one switching unit concentrically mounted withrthe axis of said shaft; said switching unit comprising a commutator ring and a rotatably mounted roller; said commutator ring carrying a plurality of insulated, conductingarcuate seg ments; said roller being a frusturn and having an outer porousmetallic shell, said roller. and said commutator ring having a line of contact rollable with the rotation of said shaft; a pump having a rotor and a stator both concentrically mounted with the axis of said main shaft; said rotor fitting inside said stator and being separated therefrom by a narrow gap to allow for the frictional circulation of said fluid between the outer rim of said rotor and the inner rim of said stator; and said stator comprising at least one inlet port, at least one outlet port, and a filter spaced in the path of liquid flow from the outlet port to the inlet port forremoving foreign particles from said fluid.

4. A commutator comprising in combination: a hou ing, a rotatable main shaft in said housing, at least one switching unit concentrically mounted with the axis of said'shaft, said switching unit comprising a commutator ring and a. rotatably mounted roller; said commutator ring carrying a plurality of insulated, conducting, arcuate segments; said roller being a frustum having an outer,

metallic shell; said rotor and said commutator ring hav-- ing a line of contact rollable with the rotation of said shaft; a low viscosity fluid in said housing; a pump having a rotor and a stator both concentrically mounted with the axis of said main shaft, said rotor fitting mside said stator and being separated therefrom by a narrow gap to allow for the frictional circulation of said fluid between said rotor and said stator. 1 I

5. The commutator of claim 4 wherein said fluid is silicone oil and said pump further includes a filter for removing foreign particles from said fiuid.

6. The commutator of claim 4 wherein the metal of said shell is porous and said switching unit further includes a collector ring concentrically mounted with the axis of said main shaft and in substantially parallelspaced relation with said commutator ring, whereby current between selected ones of said commutator ring and said collector ring flows only through said outer metallic shell.

7. A commutator comprising in combination: a housing, a rotatable main shaft in said housing, said housing being filled with a cleaning fluid; at least one pair of switching units concentrically mounted with the axis of said shaft; each switching unit comprising a commutator ring, a collector ring in substantially parallel-spaced'relation with said commutator ring, and a rotatably mounted roller; a pump sandwiched between said switching units, said pump including a filter, a rotor and a stator roller having an outer, porous, metallic shell; and a pump having filtering means, said pump being sandwiched between said switching units and including a rotor and a stator, both concentricaly mounted with the axis of said main shaft, said stator having at least one'inlet port and at least one outlet port for circulating said liquid upon the occurrence of a relative rotation between said rotor and said stator.

9.-A commutator comprising in combination: a housa liquid filling said housing, a rotatable main shaft in said housing, at least one pair of switching units concentrically mounted with the axis of said shaft; each switching unit comprising a commutator ring, an annular collector ring insulated from and in substantially parallel-spaced relation with said commutator ring, and a rotatably mounted roller resiliently biased toward said rings; said commutator ring carrying a plurality of insulated, conducting segments, said roller having an outer, metallic, porous Y shell; 2. pump sandwiched between said switching units, said pump including a rotor, a stator, and a filter carried by said stator for removing foreign particles from said liquid and for maintaining a low contact resistance between said shell and said commutator and collector rings.

10. In a commutator, a housing, a low viscosity liquid filling said housing, a rotatable main shaft in said housing, a motor coupled with said shaft, at least one pair of switching units concentrically mounted with the axis of said shaft; each switching unit comprising a commutator ring, a collector ring, and a rotatably mounted roller resiliently biased toward said rings; said commutator ring carrying a plurality of insulated, conducting, arcuate segments, said collector ring being insulated from and in substantially parallel-spaced relation with said commutator ring; a pump sanwiched between said switching units, said pump including a cylindrical rotor, an annular stator, both concentrically mounted with the axis of said main shaft whereby a flow of liquid is established when said motor is energized by a driving power source.

11'. In a commutator, a housing, a low viscosity silicone oil filling said housing, a rotatable main shaft in said housing, a motor coupled with said shaft, at least one pair of switching units concentrically mounted with the axis of said shaft; each switching unit comprising a commutator ring, an annular collector ring, and a roller; said commutator ring carrying a plurality of insulated, conducting, arcuate segments; said collector ring being insulated from and in substantially parallel-spaced relation with said commutator ring; an auxiliary shaft for rotatably carrying said roller, resilient, biasing means urging said roller against said commutator and collector rings; said roller including an outer, porous, conducting shell; a pump sandwiched between said switching units,

said pump including a cylindrical rotor, an annular stator, both concentrically mounted with the axis of said main shaft, said stator having at least one inlet port and one outlet port, and a filter spaced in the path of flow of said oil from said outlet port to said inlet port whereby a low resistance path is maintained between each of said both concentrically mounted with the axis of said main I shaft whereby a flow of fluid is established upon the occurrence of a relative rotation between said rotor and said stator.

, 8. A commutator comprising in combination: a housing, a rotatable main shaft in said housing, said housing being filled with a low viscosity liquid; at least one pair segments and said collector ring only through said shell.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Sauer: Uses of Commercial Silicone Products; General Electric Rev., June 1951; pp. 39-44 relied upon. 

10. IN A COMMUTATOR, A HOUSING, A LOW VISCOSITY LIQUID FILLING SAID HOUSING, A ROTATABLE MAIN SHAFT IN SAID HOUSING, A MOTOR COUPLED WITH SAID SHAFT, AT LEAST ONE PAIR OF SWITCHING UNITS CONCENTRICALLY MOUNTED WITH THE AXIS OF SAID SHAFT; EACH SWITCHING UNIT COMPRISING A COMMUTATOR RING, A COLLECTOR RING, AND A ROTATABLY MOUNTED ROLLER RESILIENTLY BIASED TOWARD SAID RINGS; SAID COMMUTATOR RING CARRYING A PLURALITY OF INSULATED, CONDUCTING, ARCUATE SEGMENTS, SAID COLLECTOR RING BEING INSULATED FROM AND IN SUBSTANTIALLY PARALLEL-SPACED RELATION WITH SAID COMMUTATOR RING; A PUMP SANWICHED BETWEEN SAID SWITCHING UNITS, SAID PUMP INCLUDING A CYLINDRICAL ROTOR, AN ANNULAR STATOR, BOTH CONCENTRICALLY MOUNTED WITH THE AXIS OF SAID MAIN SHAFT WHEREBY A FLOW OF LIQUID IS ESTABLISHED WHEN SAID MOTOR IS ENERGIZED BY A DRIVING POWER SOURCE. 